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wjschmidt (Bill Schmidt)
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Apr 4 2022, 3:15 PM (11 w, 6 d)

Recent Activity

Wed, Jun 15

wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Wed, Jun 15, 7:11 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Wed, Jun 15, 7:00 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Wed, Jun 15, 6:53 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Wed, Jun 15, 6:37 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Wed, Jun 15, 6:25 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Wed, Jun 15, 6:20 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Wed, Jun 15, 6:19 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Wed, Jun 15, 6:14 AM · Restricted Project, Restricted Project

Tue, Jun 14

wjschmidt updated the diff for D125987: [SLP] Account for cost of removing FMA opportunities.

Rebased; fixed pasto in getFMACostSavings(); ensured that getFMACostSavings() returns nonnegative values; and made a slight simplification in adjustForFMAs(). Thanks!

Tue, Jun 14, 2:34 PM · Restricted Project, Restricted Project

Fri, Jun 3

wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
Fri, Jun 3, 7:00 AM · Restricted Project, Restricted Project

May 25 2022

wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
May 25 2022, 9:56 AM · Restricted Project, Restricted Project

May 23 2022

wjschmidt updated the diff for D125987: [SLP] Account for cost of removing FMA opportunities.

This revision now includes fixes for both cases: a horizontal reduction of fadds fed by a vectorized tree rooted at fmuls, and a vectorized tree of fmuls that feeds arbitrary fadds and/or fsubs. It was misguided to break this up into two patches without showing you both...

May 23 2022, 6:24 AM · Restricted Project, Restricted Project

May 19 2022

wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
May 19 2022, 11:03 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
May 19 2022, 10:06 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
May 19 2022, 9:56 AM · Restricted Project, Restricted Project
wjschmidt added a comment to D125987: [SLP] Account for cost of removing FMA opportunities.

On what target are you seeing this problem?

May 19 2022, 9:54 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D125987: [SLP] Account for cost of removing FMA opportunities.
May 19 2022, 9:54 AM · Restricted Project, Restricted Project
wjschmidt added a comment to D125987: [SLP] Account for cost of removing FMA opportunities.

I think this loss is not only relevant for horizontal reductions, but can pessimize things in general, right?

May 19 2022, 9:39 AM · Restricted Project, Restricted Project
wjschmidt requested review of D125987: [SLP] Account for cost of removing FMA opportunities.
May 19 2022, 9:32 AM · Restricted Project, Restricted Project
wjschmidt added a comment to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

You're welcome! Thanks for the good advice!

May 19 2022, 8:49 AM · Restricted Project, Restricted Project
wjschmidt committed rGd633dbd19573: [SLP][NFC] Pre-commit test showing vectorization preventing FMA (authored by wjschmidt).
[SLP][NFC] Pre-commit test showing vectorization preventing FMA
May 19 2022, 6:59 AM · Restricted Project, Restricted Project
wjschmidt closed D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.
May 19 2022, 6:58 AM · Restricted Project, Restricted Project

May 18 2022

wjschmidt added a comment to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

LG with some nits

May 18 2022, 2:48 PM · Restricted Project, Restricted Project
wjschmidt updated the diff for D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

Thanks for the helpful comments to date! In this version, I've managed to remove the undefs from the original test. I also added a second test that removes the loop structure. For both tests, today we will generate an unprofitable horizontal reduction. With the first test, adding cost modeling to constrain the horizontal reduction allows FMAs to be generated. With the second test, this is insufficient, as we then decide to vectorize the multiplies in an unprofitable way. The two tests demonstrate the need to account for lost FMAs in the cost modeling both when vectorizing for a reduction and when vectorizing a list of multiplies.

May 18 2022, 9:49 AM · Restricted Project, Restricted Project

May 17 2022

wjschmidt added a comment to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

The undefs still here.

Yes, see above -- I was unable to find a sequence without the undefs that causes the horizontal reduction to kick in.

Use -slp-threshold option to avoid problems with the cost.

May 17 2022, 7:18 AM · Restricted Project, Restricted Project

May 11 2022

wjschmidt added a comment to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

Also, why these sequences are not optimized by InsrtuctionCombiner to FMA?

Phase ordering -- it seems the FMA combining happens quite late in the pipeline. When we replace the adds with a horizontal reduction, the opportunity is removed.

Why, could you investigate it?

I'll have to refresh my memory, but my recollection is that the FMA combining is done in the MI level instruction combiner.

Why? Are there any target-caused limitations?

May 11 2022, 8:11 AM · Restricted Project, Restricted Project
wjschmidt added a comment to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

Also, why these sequences are not optimized by InsrtuctionCombiner to FMA?

Phase ordering -- it seems the FMA combining happens quite late in the pipeline. When we replace the adds with a horizontal reduction, the opportunity is removed.

Why, could you investigate it?

May 11 2022, 7:48 AM · Restricted Project, Restricted Project
wjschmidt added a comment to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

The undefs still here.

May 11 2022, 7:24 AM · Restricted Project, Restricted Project

May 10 2022

wjschmidt added a comment to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

Hi! I'd like to ping this revision, please.

May 10 2022, 6:31 PM · Restricted Project, Restricted Project

May 4 2022

wjschmidt updated the diff for D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

I've made all requested changes, with the exception that I can't remove the loop structure or any of the undefs without breaking the test. In both cases, we no longer generate the horizontal reduction. I've made all the reductions Alexey requested, and changed the variable names as Vasileios requested.

May 4 2022, 9:10 AM · Restricted Project, Restricted Project
wjschmidt added inline comments to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.
May 4 2022, 6:26 AM · Restricted Project, Restricted Project

May 3 2022

wjschmidt added inline comments to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.
May 3 2022, 1:03 PM · Restricted Project, Restricted Project
wjschmidt added a comment to D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.

Try to reduce test more. I think you can remove attributes, datalayout, pass triple as an argument, remove comments for incoming branches

May 3 2022, 1:01 PM · Restricted Project, Restricted Project
wjschmidt requested review of D124867: [SLP][NFC] Pre-commit test showing vectorization preventing FMA.
May 3 2022, 11:56 AM · Restricted Project, Restricted Project